/*typeof */
console.log(typeof 1,typeof NaN,typeof new Number(1));//Number类
console.log(typeof '1',typeof new String('1'));//String类
console.log(typeof true);
console.log(typeof undefined);
console.log(typeof BigInt(1n),typeof 2n);
console.log(typeof null);//早期32位用低3位"000"表示对象，而null的机器码为全0





